In some trains, electrical power may be generated at one vehicle in the train and distributed to other vehicles of the train. For example, a locomotive or a generator car may include an alternator, referred to as a head-end-power (HEP) alternator, that distributes electrical power to other cars in the train. In a passenger train for example, the electrical power generated by a HEP alternator may be distributed to passenger cars for lighting, electrical, and other hotel needs of passengers. In one example, a HEP alternator in a rail vehicle is excited by power electronics (e.g., including a battery, permanent magnets, driver circuits) that are externally positioned from the HEP alternator in the rail vehicle.
In some cases, the external power electronics that provide excitation to the HEP alternator add additional overhead to a rail vehicle. For example, the external power electronics can increase the overall cost and weight of the rail vehicle. As another example, the external power electronics may require cooling by a cooling system. The cooling system increases fuel consumption of the rail vehicle, since additional fuel is burned to generate electrical power to operate the cooling system.